Preventing Multiple Form Submits using javascript

source: http://www.elated.com/articles/preventing-multiple-form-submits/

write the below javascript code
var form_submitted = false;

function submit_form ( )
{
if ( form_submitted )
{
alert ( "Your form has already been submitted. Please wait..." );
return false;
}
else
{
form_submitted = true;
return true;
}
}



write the below function cal in html form

form onsubmit="return submit_form()"